This document discusses some of the challenges of life in the sea for marine organisms. It covers salinity, temperature, and surface-to-volume ratio. Regarding salinity, it explains that many marine organisms must regulate salt and water balance through diffusion, osmosis, and being either osmoconformers or osmoregulators. It also discusses how temperature affects organisms' metabolisms and whether they are poikilothermic or homeothermic. Finally, it notes that surface-to-volume ratio determines how easily organisms can exchange substances and that smaller organisms have a higher ratio.

1. Pannasastra University of Cambodia
Course: Marine Biology
Lecturer: Chea Leng
Topic: Challenges of Life in the Sea
Group 3
Thap Rachana
Khem Chhor Vida
Seng Bunthoeun
Seng Rithy
Soun Vattanak

2. CONTENT
I. Challenges of Life in the Sea
II. Salinity
– Diffusion and Osmosis
– Regulation of Salt and Water Balance
III. Temperature
IV. Surface-to-Volume Ratio

3. CHALLENGES OF LIFE IN THE SEA

4. SALINITY
• Salinity is the saltiness or
dissolved salt content of a body of water.
• Many enzymes and other organic molecules
are very sensitive to change in the
concentrations of the ions that are common in
seawater.

5. • Salinity in rivers, lakes, and the ocean is
conceptually simple, but technically
challenging to define and measure precisely.
Conceptually the salinity is the quantity of
dissolved salt content of the water.

7. Salinity Change of Ocean

8. DIFFUSION
 Diffusion is a spontaneous
movement of particles from
an area of high concentration
to an area of low
concentration.
 Goes from a high concentration gradient to a low
concentration gradient.
 Does not need water for movement.
http://163.178.103.176/Fisiologia/gen_pracb_dinamica3.html

9. DIFFUSION
 Diffusion mainly occurs in
gaseous state or within
gas molecules and liquid
molecules.
• Example: The molecules of 2 gases are in
constant motion and if the membrane
separating them is removed the gases will
mix because of random velocities.
http://www.diffen.com/difference/Image:Diffusion.svg

10. OSMOSIS
• Osmosis is the spontaneous net movement of
water across a semipermeable membrane from a
region of low solute concentration to a solution
with a high solute concentration, down a solute
concentration gradient.
• Moves down concentration gradient.
• Needs water for movement.

11. OSMOSIS
• It occurs when the medium
surrounding the cell has a
higher water concentration
than the cell.
• The cell gains water along
with important molecules and
particles for growth.
• It also occurs when water
and particles move from one
cell to another.
http://www.ias.ac.in/initiat/sci_ed/resources/chemistry/
physical.html

12. REGULATION OF SALT AND WATER
BALANCE
 Two major types of osmoregulation
are osmoconformers and
osmoregulators.
• Osmoconformers match their
body osmolality to their
environment actively or passively.
• Most marine invertebrates are
osmoconformers, although their
ionic composition may be different
from that of seawater.
https://en.wikipedia.org/wiki/Osmoregulation#/media/File:Bachforelle_o
smoregulatoin_bw_en2.png

13. TEMPERATURE
Temperature refers to the measured amount of heat
in a place or in the body.
 Organisms are greatly affected by temperature.
Metabolic reactions proceed faster at high
temperatures and slow down dramatically as it gets
colder.

14. Poikilotherms
• Poikilotherms are most animals,
including reptiles, fishes and
amphibians, and include
invertebrate species.
• They could not keep their body
temperature constant, instead it is
close to that of their surroundings,
so when their body temperature is
high.
– Example: On a hot summer's day, they
can be very active, but when it is low,
for example on a cold winter's night,
they can produce energy only slowly.

15. Homoiotherms
• Their living does not depend
on the temperature of their
surrounding.
• Homeotherms can keep their
body temperature almost
constant. Warm-blooded
animals are also often known
as endotherms.
• All mammals usually have a
body temperature of about
36oC and all birds usually have
a body temperature of about
42oC.

16. SURFACE-TO-VOLUME RATIO
Adaptations to salinity and temperature are needed
:
• Salt and heat can flow into and out of organism
• Exchange nutrients
• Waste products
• Gases
One thing that determines the S/V ratio is the size
of the organism
• Organisms grow larger
• Small organisms have a larger S/V ratio than big
ones
• Small organisms ( single-celled ones)

17. THANK YOU